1. Field of the Invention
The present invention relates generally to removing liquid from disks, and more particularly to apparatus and methods for drying a disk that has been wet in a liquid bath, after which the disk and the bath are separated at a controlled rate to form a thin layer of liquid on the disk as the disk is positioned in a gas-filled volume, wherein the volume is defined by a hot chamber that continuously transfers thermal energy to the disk in the volume, and wherein hot gas directed into the volume and across the disk and out of the volume continuously transfers thermal energy to the disk, so that the thermal energy transferred to the disk in the volume evaporates the thin layer from the disk without decreasing the rate of separation of the disk and the bath below a maximum rate of such separation at which a meniscus will form between the bath and the surface of the disk during such separation.
2. Description of the Related Art
In the manufacture of semiconductor devices, process chambers are interfaced to permit transfer of wafers between the interfaced chambers. Such wafer transfer is via transport modules that move the wafers, for example, through slots or ports that are provided in the adjacent walls of the interfaced chambers. For example, transport modules are generally used in conjunction with a variety of wafer processing modules, which may include semiconductor etching systems, material deposition systems, flat panel display etching systems, and wafer cleaning systems. Due to growing demands for cleanliness and high processing precision, there has been a greater need to reduce the amount of human interaction during, between, and after such processing steps. This need has been partially met with the implementation of vacuum transport modules which operate as an intermediate wafer handling apparatus (typically maintained at a reduced pressure, e.g., vacuum conditions). By way of example, a vacuum transport module may be physically located between one or more clean room storage facilities where wafers are stored, and multiple wafer processing modules where the wafers are actually processed, e.g., etched or have deposition performed thereon, or cleaned. In this manner, when a wafer is required for processing, a robot arm located within the transport module may be employed to retrieve a selected wafer from storage and place it into one of the multiple processing modules.
Despite use of such intermediate wafer handling apparatus, it is still necessary to clean and dry the wafers at the completion of such processing. As an example, after the wafers have been cleaned, the wafers may have a non-uniform coating of liquid. A wafer with such non-uniform coating of liquid, or with one or more drops of liquid thereon, or with any liquid thereon in any physical form, may be said to be xe2x80x9cwetxe2x80x9d. In contrast, a wafer having a uniform coating of liquid may be said to be xe2x80x9cuniformly wetxe2x80x9d.
In the past, items other than wafers have been processed. Items such as annular-shaped disks of many various sizes have been used for manufacturing data storage devices, for example. Such disks have also been subjected to a drying operation. After cleaning and while wet, such disks have been placed in a tank containing a bath of hot liquid. In one type of drying operation, the hot liquid has been drained from the tank at a rate such that a thin layer of liquid, rather than one or more drops of liquid, forms on that portion of such disk that is out of the draining liquid. The thin layer has been preferred over one or more drops because a drop of liquid has a high volume, e.g., from about 0.001 ml. to about 0.020 ml. In comparison to the drop, a thin layer of liquid on a substrate such as a 95 mm diameter disk, may only have a volume of at the maximum diameter of the disk of about 0.0007 ml, for example. Evaporation of a drop generally results in the concentration of small particles at the last small point on the disk at which the drop exists. Such concentration may result in defects in a data storage device made from the disk.
To remove the thin layer from such disk, reliance has been placed on the thermal energy stored in such disk to provide the thermal energy necessary to evaporate the thin layer. However, it appears that using only such stored thermal energy, the thin layer may evaporate from the disk at a rate less than the maximum rate of separation of the liquid bath and the disk at which a meniscus will form between the liquid bath and the surface of the disk during such separation. Thus, the rate at which the liquid is drained from the tank has to be decreased to match the rate of evaporation. Alternatively, the disk would have to be retained in the tank after the draining has been completed. Each of such decreased rate of draining and such retaining increases the time required to dry the disk, which increases the cost of fabricating devices based on the disk.
In view of the forgoing, what is needed is apparatus and methods of efficiently drying disks. Such efficient drying should allow the disks and the liquid to be separated at a rate no less than the maximum rate of separation of the liquid and the disk at which a meniscus will form between the liquid bath and the surface of the disk. Also, the efficient drying should rapidly remove from the disk a thin layer of liquid that forms on the disk as the disk and the bath are separated, wherein xe2x80x9crapidlyxe2x80x9d means such removal occurs before the disk and the bath have been completely separated e.g., separated by about 0.004 inches.
Broadly speaking, the present invention fills these needs by providing apparatus and methods of efficiently removing fluid from disks. The efficient removing is attained by providing apparatus and methods for drying a disk that has been uniformly wet in a fluid bath, in which the disk and the bath are separated at a controlled rate to form a thin layer of fluid on the disk as the disk is positioned in a gas-filled volume. In addition to such separation, the efficient removing is attained by defining the gas-filled volume by use of a hot chamber that continuously transfers thermal energy to the disk in the volume. Further, hot gas directed into the volume and across the disk and out of the volume continuously transfers thermal energy to the disk. The directing of the gas out of the volume is independent of the separation of the bath and the disk. The thermal energy transferred to the disk in the volume evaporates the thin layer from the disk without decreasing the rate of separation of the disk and the bath below the maximum rate of such separation at which a meniscus will form between the bath and the surface of the disk during such separation. In addition to such separation and directing of the hot gas across the disk and out of the volume, the relative humidity in the volume is kept low to inhibit recondensation of the fluid on the disks, for example.
Such efficient removal enables the disk throughput of such apparatus and method to be limited only by the type of disk that is being dried, and the type of fluid used to wet the disk. For example, the characteristics of particular types of disks and fluid dictate the maximum rate of such separation of the disk and the bath at which a meniscus will form between the bath and the surface of the disk during such separation and the disk will be uniformly wet.
In one embodiment of the present invention a disk drying system may include a bath enclosure configured to hold a fluid so that the fluid defines a top fluid surface. A temperature and humidity-controlled chamber may also be defined above the fluid surface. The chamber has a first opening at a first side proximate to the fluid surface and a second opening at a second side that is opposite to the first side.
In another embodiment of the present invention the disks to be dried have opposite sides, and apparatus for drying the disks may include a bath containing hot liquid, wherein the liquid defines an upper surface. Also provided is an enclosure having an inlet spaced from the upper surface and an outlet adjacent to the upper surface. The enclosure defines a continuous gas flow path from the inlet to the outlet, the flow path extending from the inlet along the upper surface and through the outlet. A heat transfer unit may supply hot gas to the inlet, with the hot gas being under pressure so as to flow in the continuous flow path. The heat transfer unit may transfer thermal energy to the enclosure so that the enclosure radiates thermal energy across the continuous flow path. A disk carrier may be movable in the bath and in the enclosure for moving the disk at a controlled rate out of the bath and into intersection with the continuous flow path. The rate may be controlled so that as the disk moves out of the bath a thin layer of the liquid is formed on each of the opposite sides of the disk. As the disk intersects the continuous flow path thermal energy from the hot gas and from the enclosure is received by the disk and by the thin layer. The received thermal energy evaporates the thin layer off the opposite sides of the disk.
In a related embodiment, the walls of the enclosure may define a perimeter of the enclosure. A plenum surrounds the perimeter of the enclosure for receiving the gas and the evaporated thin layer from the outlet. To assure that the flow path remains continuous and to control the relative humidity in the enclosure, a fan is provided for exhausting the gas, the evaporated thin layer, and vapor from the bath from the plenum. In a further embodiment, apparatus provided for drying a disk having opposite planar sides may include a bath for containing a fluid having an upper surface. A heat transfer chamber may have a plurality of walls, each of the walls having a bottom at generally the same level as the level of adjacent ones of the walls. The chamber defines a disk drying volume above the bottoms of the walls and within which a disk drying path extends. At least one of the walls is provided with a gas inlet positioned opposite to the bottom. A support may suspend the chamber above the bath with the disk drying path starting adjacent to the fluid surface and extending to a point adjacent to the gas inlet. The support positions the bottoms of the chamber walls spaced from the liquid surface to define an elongated outlet extending around the disk drying path. A hot gas supply may be connected to the gas inlet for flowing hot gas through the chamber across the opposite planar sides of the disk and out of the chamber through the elongated outlet to continuously transfer thermal energy at a selected temperature across the disk drying path, and thus to the disk and the thin film on the disk. A heater connected to the chamber between the gas inlet and the elongated outlet may radiate thermal energy across the disk drying path, and also to the disk and the thin film on the disk.
In a still other embodiment, a method for drying a disk may include an operation of introducing a disk being in a wet state into a fluid bath. The disk is removed from the fluid bath at a controlled rate along a selected path. Heated gas is applied to the disk as the disk is moved along the selected path and out of the fluid bath. Advantageously, the applied heated gas flows in at least one continuous flow path to the disk without recirculating the heated gas to the disk. In this manner, the applied heated gas transitions the disk to a dry state as the disk exits the fluid bath. A related feature is that thermal energy is radiated onto the disk as the disk moves along the selected path out of the fluid bath. In another related aspect of this method embodiment, an enclosure is provided to define the at least one continuous flow path. The applying of the heated gas may include flowing hot nitrogen in the at least one continuous flow path across the disk to effect the transition by evaporating the fluid from the disk into the hot nitrogen. The applying operation then removes the hot nitrogen and the evaporated fluid from the enclosure and away from the fluid bath. In this manner, the hot nitrogen and the evaporated fluid are not recirculated in the enclosure, such that the evaporated fluid does not accumulate, which accumulation would reduce the rate at which the evaporation takes place and foster recondensation of the fluid on the disks.
In yet another embodiment of the present invention a method for drying a disk may cause a disk to be immersed in a fluid bath to wet opposite sides of the disk with the fluid. Then the disk is moved out of the fluid bath into a defined volume along a selected path. The moving may be controlled to allow a meniscus on each of the opposite sides to form and leave a thin film of the fluid on the opposite sides of the disk as the disk moves from the fluid bath. By directing radiant energy into the thin film of the fluid on the opposite sides of the disk, and by flowing heated gas into the defined volume and along the disk as the disk is moved along the selected path out of the fluid bath, the thin film of the fluid is evaporated from the disk and combines with the heated gas flowing along the disk. An exit from the defined volume is provided for the combined removed thin film of the fluid and the gas. Advantageously, the combination of the radiant energy, the heated gas and the exit promote rapid evaporation of the thin film and foster a decrease in the time required to dry the disks.
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.